TESS photometry of helium-rich hot subdwarfs: r modes in BD+37 442 and BD+37 1977

Abstract

TESS photometry of the extremely helium-rich hot subdwarfs BD+37 442 and BD+37 1977 demonstrates multi-periodic low-amplitude variability with principal periods of 0.56 and 1.14 d, respectively, and with both first and second harmonics present. The lightcurves are not perfectly regular, implying additional periodic and/or non-periodic content. Possible causes are examined, including the binary hypothesis originally introduced to explain X-ray observations, differentially rotating surface inhomogeneities, and pulsations. If the principal photometric periods correspond to the rotation periods, the stars are rotating at approximately 0.7 and 0.3 x breakup, respectively. Surface Rossby waves (r modes) therefore provide the most likely solution.

arXiv commentMNRAS accepted, 6 pages, 3 figures

References in corpus (16)

• Gaia Data Release 2. Summary of the contents and survey properties
• Hot subluminous stars
• The interior rotation of a sample of gamma Doradus stars from ensemble modelling of their gravity mode period spacings
• Theory and evidence of global Rossby waves in upper main-sequence stars: r-mode oscillations in many Kepler stars
• Double white dwarf mergers and elemental surface abundances in extreme helium and R Coronae Borealis stars
• Post-merger evolution of carbon-oxygen + helium white dwarf binaries and the origin of R Coronae Borealis and extreme helium stars
• On helium-dominated stellar evolution: the mysterious role of the O(He)-type stars
• Radial pulsation as a function of hydrogen abundance
• Time-series photometry of the O4 I(n)fp star zeta Puppis
• Discovery of spin-up in the X-ray pulsar companion of the hot subdwarf HD 49798
• On the angular momentum evolution of merged white dwarfs
• Discovery of a compact companion to the hot subdwarf star BD+37 442
• The distance, rotation, and physical parameters of zeta Pup
• Follow-up observations of X-ray emitting hot subdwarf star: the He-rich sdO BD +37° 1977
• TESS photometry of extreme helium stars PV Tel and V821 Cen
• The lack of X-ray pulsations in the extreme helium star BD+37${}^{\circ }$442 and its possible stellar wind X-ray emission

Cited by in corpus (4)

• Hot subdwarf Atmospheric parameters, Kinematics, and Origins -- Based on 1587 hot subdwarf stars observed in Gaia DR2 and LAMOST DR7
• EVR-CB-004: An Inflated Hot Subdwarf O star + Unseen WD Companion in a Compact Binary Discovered with the Evryscope
• Unresolved Rossby and gravity modes in 214 A and F stars showing rotational modulation
• Rossby waves on stellar equatorial beta-planes: uniformly rotating radiative stars